Defining high aspect ratio structures with controllable sidewalls in silicon has become increasingly important both in the nanometer and micrometer scale for solar cells, microelectronic devices, and chemical analysis. High aspect ratio micrometer pillars are used for solar cell investigations while nanometer scale high aspect ratio pillars are enabling fundamental investigations in theories of nanoscale pillar stress mechanics, silicon based lasers, and nanoscale electronic devices such as finFETs. Currently various nanofabrication techniques exist that rely on self assembly or bottom-up processing. Some top-down processing enabling reproducibility in nanofabrication can also be found.
Further applications are high surface area chemical sensors, mechanical oscillators and piezo-resistive sensors. High aspect ratio pillars with diameters between 50-100 nm could prove useful for core-shell type plasmonic resonators while pillars with sub-10 nm diameters have shown promising light emission characteristics.